Issue17 ozone

sis_17_RZ_.qxq:Layout 1 24.11.2010 9:40 Uhr Seite 46

Im
ag
e
co
ur

te
sy
of
NA
AS
A hole
in the sky
Twenty-five years ago,
the discovery of the
hole in the ozone layer
hit the news. How have
things developed since?
Tim Harrison and Dudley
Shallcross investigate.
The Antarctic ozone hole at its annual maximum on
12 September 2008, stretching over 27 million
square kilometres. This is considered a moderately
large ozone hole, according to NASA

Discovering the hole
It was a serendipitous find, as Jonathan Shanklin, one of
the hole’s discoverers, remembers: having joined the 35
British Antarctic Surveyw1 in 1977, he was supposed to
digitise their backlog of ozone measurements – until then, 30
handwritten data sheets. As it turned out, this included
the crucial decade, the 1970s, when ozone levels began to
Altitude (kilometres)

25 Stratospheric
Public domain image; image source: Wikimedia Commons

drop. Ozone layer ozone
There had already been growing concern that industrial
20
chlorofluorocarbons (CFCs) – organic compounds such as
trichlorofluoromethane (CFCl3) and dichlorodifluo-
romethane (CF2Cl2), then widely used as refrigerants, pro- 15
pellants (in spray cans) and solvents – might destroy the
ozone layer. For an open day in 1983, Shanklin prepared a 10
Ozone Tropospheric
graph – ironically to show that the ozone data from that increases ozone
year were no different from 20 years before. Although this 5 from pollution
was true for the overall ozone levels, he noticed that the
springtime values did look lower from one year to the 0
next. Further studies corroborated this, and in 1985 Ozone concentration
Shanklin and his colleagues Joe Farman and Brian
Gardiner published their findings: each Southern
Ozone is present throughout the lower atmosphere. Most
Hemisphere spring, a hole gaped in the ozone layer above
ozone is in the stratospheric ozone layer. Near Earth’s surface,
the Antarctic, it was probably caused by CFCs, and it was the ozone levels increase as a result of pollution from human
growing (Farman et al., 1985). activities

46 Science in School Issue 17 : Winter 2010 www.scienceinschool.org

Science topics

What is the chemistry behind this, and why is the ozone (hν) with a wavelength (l) around 200 nm and dissociates
hole dangerous? into two oxygen atoms (O•) (reaction 1). Each of these can
then combine with another oxygen molecule to form
ozone in the stratosphere ozone, if the pressure (M) is high enough (approximately
Ozone (O3) is a much less stable triatomic form of oxy- one thousandth of an atmosphere) to stabilise the newly
gen (O2). It is a pale blue gas present at low concentrations formed ozone molecule (reaction 2). The higher the alti-
throughout the atmosphere – and a double-edged sword: tude, the faster the rate of reaction 1 (below 20 km alti-
in the troposphere (see image on page 48), ozone is an air tude, no 200 nm photons occur because they have all been
pollutant which can damage the respiratory systems of absorbed in reaction 1). The rate of reaction 2, however, is
humans and other animals and burn sensitive plants. The faster closer to the ground, where atmospheric pressure is
ozone layer in the stratosphere, however, is beneficial, pre- higher. As a result, the maximum amount of ozone is cre-
venting most of the harmful ultraviolet (UV) light emitted ated between about 25 and 30 km altitude (see graph on
by the Sun from reaching Earth’s surface. page 46).
The rate of ozone formation maximises in the strato- The stratosphere has two important consequences for
sphere, the second highest layer of Earth’s atmosphere (at life on Earth. First, ozone itself absorbs high-energy
about 10-50 km altitude; see image), through a photo- UV radiation at around 250 nm
chemical mechanism: (reaction 3):
O2 + hν → O• + O• l ~ 200 nm (1) O3 + hν → O• + O2 l ~ 250 nm DH = - 90 kJ mol-1 (3)
O• + O2 + M → O3 + M (2) Between them, oxygen (reaction 1) and ozone (reaction
An oxygen molecule (O2) absorbs a photon of UV light 3) therefore filter out of the atmosphere most of the short-

Chemistry
Earth science catalytic cycles. Where do those organisms live?
Ages 16+ Which chemical substances do they produce?
· The chemical composition of the atmosphere and
The ozone hole is a topical global issue, and you will its influence on the climate. Which gases is the
find this article really helpful to get into the subject. atmosphere composed of? In which way do the
The chemical processes involved are described in atmosphere’s properties determine climatic con-
full detail. In chemistry lessons, the article can be ditions on Earth’s surface, and how does this dif-
used to teach atomic structure and chemical bonds, fer on other planets?
free radicals, catalytic cycles, and the influence of The article could also form the basis of a lesson on
light and temperature on chemical reactions. how science is reported in the media. Students could
compare this article to those in the general press: do
For the earth science classroom, the article would fit
they provide a balanced view of the question, men-
in the context of the following topics:
tioning both chemical and natural components lead-
· Atmospheric influence on climate ing to the formation of the ozone hole? Do they min-
· Biological processes occurring on Earth’s surface imise or overemphasise the phenomenon as a
and affecting marine organisms whole? Why – due to journalists’ ignorance, political
· Earth’s morphology and the distribution of moun- strategy or both? For further ideas on using news in
tain ranges on Earth’s surface the science classroom, see Veneu-Lumb & Costa
· The changing of the seasons, Earth’s axial tilt and (2010).
rotation. Finally, the text is suitable as the basis of a compre-
REViEW

There is the opportunity for interdisciplinary work hension exercise, too. Possible questions are:
linking chemistry and earth sciences. Possible topics
include:
· Why is this topic a much debated question
nowadays?
· The geographical distribution of the organisms · What is the role of natural factors in the growth
that produce chemicals that are active in natural of the ozone hole? What about human factors?
Teresa Celestino, Italy

www.scienceinschool.org Science in School Issue 17 : Winter 2010 47


Image courtesy of Marlene Rau

Layers of atmosphere leading to space

10 000 km
Exosphere

690 km

The four main reactions of oxygen in the ozone layer. Blue arrows indicate reac-
tions, green dotted arrows indicate that a molecule from one reaction goes on to
take part in another reaction. M denotes the pressure required for reaction 2

wave UV radiation between 200 and 300 nm, which would otherwise be very
damaging to life on Earth.
Second, reaction 3 produces a lot of heat, so the stratosphere is a warmer
layer than the top of the troposphere (see image left), making the weather in
the troposphere less extreme than it would otherwise be.
Thermosphere

Reactions 2 and 3 rapidly interconvert oxygen atoms and ozone. There is
another slow reaction, though, which is known to destroy both oxygen atoms
and ozone, namely the reaction between these two species:
O• + O3 → O2 + O2 (4)
Reactions 1-4 are summarised in the diagram above.
85 km

Natural catalytic cycles reduce the levels of ozone
Mesosphere

In 1995, Paul Crutzen, Mario Molina and F Sherwood Rowland were awarded
the Nobel Prize in Chemistry for their work on the formation and decomposi-
tion of ozone in the stratosphere. What had they learned? In the 1970s, Crutzen
and others discovered the existence of natural catalytic cycles that speed up
50 km reaction 4 and reduce the amount of ozone in the stratosphere (Crutzen, 1970,
1971): water (H2O), methane (CH4), nitrous oxide (N2O) and chloromethane
(CH3Cl) are released into the atmosphere from biological processes occurring on
Stratosphere

Earth’s surface, and lead to the formation of radicals such as hydroxyl (OH•),
nitric oxide (NO•) and chlorine (Cl•), which catalyse the decomposition of ozone.
Reaction 5 shows how chloromethane releases chlorine radicals into the strat-
osphere through photolysis, and reactions 6 and 7 are an example of a catalytic
6-20 km
cycle (see diagram on page 49). The reactions of the other catalysts are analo-
gous with reactions 6 and 7. Chloromethane is released in part by both marine
Troposphere

and terrestrial organisms, such as red macroalgae, white rot fungi and higher
plants, to regulate chloride ion levels in the cells and – after 30 to 40 years – can
reach the upper stratosphere (around 40 km altitude) where it is broken down
0 km
by sunlight (photolysis):



Science topics

Image courtesy of Marlene Rau

Chlorine radicals
(for example from
reaction 5) enter a
catalytic cycle
(reactions 6 and 7)
of net ozone
decomposition,
which can be ter-
minated by reac-
tions 8 and 9. Blue
arrows indicate
reactions, green
dotted arrows indi-
cate that a mole-
cule from one reac-
tion goes on to take
part in another
reaction. M denotes
the pressure
required for reac-
tion 9

CH3Cl + hν → •CH3 + Cl• λ~ 200 nm (5) predicted that CFCs would cause a significant additional
The resulting chlorine free radical (Cl•) can then partici- loss of ozone at around 40 km altitude (see Molina &
pate in a catalytic cycle: Rowland, 1974). However, when the ozone hole was final-
ly found in 1985, it was in fact at around 20 km altitude,
Cl• + O3 →ClO• + O2 (6)
ClO• + O• →Cl• + O2 (7) over the South Pole in the Southern Hemisphere spring-
time (see Farman et al., 1985).
Reactions 6 and 7 taken together are in fact equivalent to
It soon emerged that chlorine free radicals from the
reaction 4, but happen much faster – in the case of the
CFCs were responsible, but many questions remained
chlorine / chlorine monoxide (ClO•) radical cycle, about
unanswered. Why did the hole occur over the Pole? If it
30 000 times faster. So why do these catalytic cycles not
occurred over the South Pole, why not also over the North
destroy all the ozone? The answer lies in the termination
Pole? Why only in spring? And why was the ozone hole at
of these cycles via the formation of stable molecules:
20 km altitude instead of at 40 km, as predicted? After all,
Cl• + CH4 →•CH3 + HCl (8) CFCs could not be broken down by sunlight at an altitude
ClO• + •NO2 + M → ClONO2 + M (9) as low as 20 km, since the photon density was insufficient.
Eventually, a chlorine free radical will encounter a For the same reason, not enough oxygen atoms are pro-
methane molecule and react to form hydrochloric acid duced at this altitude for reaction 7 to occur. Many years
(HCl, reaction 8). Similarly, a chlorine monoxide radical of further research revealed the complete story.
will bind to a nitrogen dioxide radical, forming chlorine First, chlorine free radicals released from the CFCs, e.g.
nitrate (ClONO2, reaction 9) – another pressure-dependent
CFCl3 + hν→•CFCl2 + Cl• λ~ 200 nm (10)
reaction that therefore works better at lower altitudes.
Both hydrochloric acid and chlorine nitrate are very stable, could react with methane (reaction 8) forming hydrochlo-
and the removal of chlorine and chlorine monoxide radi- ric acid, or with ozone (reaction 6) forming chlorine
cals eventually stops the catalytic cycle. monoxide radicals, and through reaction 9 could subse-
quently form chlorine nitrate. This sequence of reactions
The Antarctic ozone hole puzzle would increase the concentrations of hydrocholoric acid
It was not long before scientists realised that CFCs could and chlorine nitrate at around 40 km altitude globally.
trigger a similar catalytic cycle of ozone degradation: in Each Southern Hemisphere winter, the South Pole is
1974, Molina and Rowland not only warned that levels of plunged into darkness for approximately three months.
CFCs continued to increase without regulation, but also The air in the stratosphere above the South Pole cools



All year round over the Equator,
in summer and autumn over the South Pole Early winter
The formation and dissolution of
the ozone hole over the year. 40 km (10) CFCl3 + hv (λ ~ 200 nm) → CFCl2 + Cl•
Reactions 5 to 9 happen over (6) Cl• + O3 → ClO• + O2 (8) Cl• + CH4 → CH3• + HCl
the Equator all year round, and (7) ClO• + O → Cl• + O2 (9) ClO• + NO2 → ClONO2
over the South Pole in summer
and autumn. In early winter, the 30 km HCl and
vortex forms over the South ClONO2
Pole, followed by the formation Vortex forms
of polar stratospheric clouds in
winter. In early spring, the sun- 20 km Cold and dark
shine returns, but the vortex air sinks
remains, and the reactions lead-
ing to ozone removal over the
South Pole take their course. In Equator
late spring, the vortex breaks
down, and ozone from mid-lati-
tudes can mix in

down; without UV radiation, reaction 3 does not occur, so HCl + ClONO2 →HNO3 + Cl2 polar stratospheric clouds (11)
no heat is released. The air sinks and Earth’s rotation causes This reaction can take place all winter, if it is cold
it to spin and form a vortex as it does so, like water going enough to form polar stratospheric clouds. When the sun-
down a plughole. This vortex is so strong that no air from
shine returns in spring, there are plenty of chlorine mole-
outside can get in, and no air from inside can get out. Air
cules at around 15-25 km altitude, which are photolysed to
that is rich in hydrochloric acid and chlorine nitrate from 40
produce chlorine radicals:
km altitude is drawn down into this cold and dark vortex.
Cl2 + hν→ Cl• + Cl• λ~ 350 nm (12)
In the extreme cold of the polar winter, the air in this
vortex becomes so cold that below -78°C (195 K) and at an and subsequently chlorine monoxide radicals via reaction 6.
altitude of 15-25 km, polar stratospheric clouds form from However, in the polar spring, reaction 7 (the formation
water and / or acid ice crystals. of chlorine radicals and oxygen molecules from chlorine
The first peculiar bit of chemistry is that hydrochloric monoxide radicals and oxygen radicals) is very slow, since
acid and chlorine nitrate can adsorb onto polar stratos- there are so few oxygen atoms present due to the lack of
pheric clouds and undergo a fast heterogeneous reaction 200 nm photons at this altitude, and here is where a sec-
from gaseous to solid phase, producing nitric acid (HNO3) ond peculiar piece of chemistry occurs. At low tempera-
that becomes incorporated into the ice crystals, whilst the tures, such as in the polar vortex – which is still very cold
chlorine (Cl2) is released back into the gas phase. even in spring – chlorine monoxide radicals can form a

3%
15%
HCI
Image courtesy of Andrew Ryzhkov; image source: Wikimedia Commons

CH3CI Natural

28% 3%
HCFC-22
CFC-12 CFC-113
6%

Anthropogenic CH3CCI3
10%

CFC-11 CCI1

23% 12%

Sources of stratospheric chlorine accord-
ing to the WMO / UNEP Scientific
Assessment of Ozone Depletion: 1998 Polar stratospheric clouds in Asker, Norway



Science topics

Image courtesy of Dudley Shallcross, Tim Harrison, Marlene Rau and Nicola Graf
Winter Early spring Late spring

HCl and Light returns, but vortex remains
ClONO2 (12) Cl2 + hv (λ ~ 350 nm) → Cl• + Cl• Vortex breaks down and
(6) Cl• + O3 → ClO•+ O2 ozone from mid-latitudes
Polar stratospheric
(13) ClO• + ClO• → ClOOCl can mix in
clouds form
(14) ClOOCl + hv (λ ~ 300 nm) → Cl•+Cl•+O2
(11) HCl + ClONO
→ HNO3 + Cl2

South Pole

dimer, chlorine peroxide (ClOOCl): In late spring, the flow of ozone-rich air from above
ClO• + ClO•→ ClOOCl (13) eventually warms the vortex via reaction 3, allowing the
This dimer is unstable at room temperature but forms vortex to eventually break down. Since exchange with
quite readily at low temperatures (below -30 °C) and can other parts of the atmosphere then becomes possible
be photolysed: again, the ozone hole is filled with ozone from the sur-
ClOOCl + hν→ Cl•+O2+Cl• λ~ 300 nm (14) rounding air.
So even though reaction 7 cannot occur, reaction 14 In some years, the ozone hole over Antarctica has grown
provides a way to regenerate chlorine free radicals with large enough to reach Australia, New Zealand, Chile and
the help of light, and the catalytic cycle for ozone deple- Argentina, growing to 1.5 times the size of the USA; and
tion can start in earnest now that the sunshine has when the ozone hole breaks up, the ozone-depleted air
returned. drifts out into nearby (populated) areas, including South
In what way does this differ from the natural catalytic Africa. For the people in these countries, the ozone hole
cycles we looked at before – why is there a total removal poses a direct health threat. The main concern is the
of ozone at some altitudes in this vortex? First, reaction 8 increased exposure to UV, which may cause skin cancer
(which removes chlorine radicals and can terminate the and ocular cortical cataracts, as well as damage to the
cycle) is very slow at the low temperatures found in the immune system. Furthermore, excessive UV radiation
vortex, and therefore ineffective. Second, all the nitrogen damages plants and building materials.
dioxide required for reaction 9 (which could likewise ter-
minate the cycle, through the formation of ClONO2) has CFCs and ozone today
been converted to nitric acid throughout the winter (e.g. Today, we have a good understanding of the physics
through reactions 9 and 11) and it is not available to be and chemistry governing the ozone layer. Once the true
regenerated since there is no upward flow in the vortex (at impact of CFCs on ozone depletion became apparent, gov-
the base of the vortex, air flows from the South Pole to the ernments passed regulations to stop the use of CFCs,
Equator, where the upward flow takes place). Therefore replacing them with alternative, shorter-lived, species
the cycle carries on unchecked and destroys all the ozone (hydrofluorocarbons and hydrochlorofluorocarbons),
at that level. Finally, without ozone, reaction 3, which which were to be phased out eventually too: the Montreal
would otherwise warm this region, is absent, and so the Protocol of 1987 and especially its amendments in 1990
vortex lasts well into the spring, exacerbating the ozone and 1992, which speeded up the phase-out, were an envi-
depletion. ronmental success.
The only reason that the ozone hole is more severe over The most recent data from AGAGE (The Advanced
the South Pole than the North Pole is that the spring tem- Global Atmospheric Gases Experiment)w2, which has been
peratures in the stratosphere above the North Pole are monitoring levels of CFCs and their replacements since
slightly warmer than those above the South Pole, because 1978, shows that even the atmospheric levels of dichlorod-
there are more mountain ranges in the mid to high lati- ifluoromethane (CF2Cl2), the longest-lived CFC, are now
tudes of the Northern Hemisphere, which change the decreasing: the legislation has been effective (see graph on
dynamics of atmospheric flow, so there are fewer polar page 52). An ozone hole still forms each spring over the
stratospheric clouds. South Pole, but estimates are that by 2050 this will no



Image courtesy of AGAGE

longer happen, and that by 2080 the
global ozone will return to 1950s levels. The atmospheric con- 550
centration of CFCs
The ozone hole is the result of an

CF2Cl2 mole fraction (ppt)
increased rapidly and is 490
increased use of CFCs, which began now slowly decreasing
in the 1930s – like any other gas, again. Data are given 430
CFCs take 30-40 years to reach the for CF2Cl2 , at the five
upper stratosphere, which means that AGAGE surface meas- 370
there is a corresponding lag in their urement stations from
effect on the ozone layer. We are cur- 1978 to the present day, 310
taken from the AGAGE
rently experiencing the stratospheric
websitew2 in September 250
chlorine peak resulting from the high- 2010 1980 1985 1990 1995 2000 2005 2010
est levels of CFC use in the 1980s – so
the maximum size the ozone hole I Ireland I Oregon / California I Barbados I Samoa I Tasmania

reaches each year should begin to
decrease a few years from now.
Although recovery is slow, we have Molina MJ, Rowland FS (1974) including CFCs and most non-CO2
definitely stopped a disaster: scien- Stratospheric sink for chlorofluo- greenhouse gases specified in the
tists have calculated that if the use of romethanes – chlorine atomic- Kyoto protocol. To access their data
CFCs had continued at its 1970s catalysed destruction of ozone. and for more information, see:
growth rate of 3% per year, this Nature 249: 810-812. doi: http://agage.eas.gatech.edu
would have led to a global ozone hole 10.1038/249810a0
Resources
by 2060, with all the health problems The article is freely accessible on the
that would bring (see image on page Nature website (www.nature.com) Sidney Chapman first derived the
53; Newman et al., 2009). or using the direct link: photolytic mechanism by which
Perhaps the most important lesson http://tinyurl.com/2u69cul ozone is formed and degraded. See:
to be learned from the ozone hole is Newman PA et al. (2009) What would Chapman S (1930) On ozone and
just how quickly our planet can have happened to the ozone layer if atomic oxygen in the upper
change as a result of human impact – chlorofluorocarbons (CFCs) had not atmosphere.
especially for the worse, but also for been regulated? Atmospheric Philosophical Magazine Series 7
the better – and that change is possi- Chemistry and Physics 9: 2113-2118. 10(64): 369-383. doi:
ble if we take action concertedly, doi: 10.5194/acp-9-2113-2009 10.1080/14786443009461588
effectively and quickly.
Patterson L (2010) A chemical bond: Jonathan Shanklin, one of the
References Nick Barker, linking schools and scientists who discovered the
universities in the UK. Science in ozone hole, published his reflec-
Crutzen PJ (1970) Influence of nitro-
School 15. www.scienceinschool.org tions 25 years after the discovery:
gen oxides on atmospheric ozone
/2010/issue15/nickbarker
content. Quarterly Journal of the Shanklin J (2010) Reflections on the
Veneu-Lumb F, Costa M (2010) Using ozone hole. Nature 465: 34-35. doi:
Royal Meteorological Society 96: 320-
news in the science classroom.
325. doi: 10.1002/qj.49709640815 10.1038/465034a.
Science in School 15: 30-33.
Crutzen PJ (1971) Ozone production www.scienceinschool.org/2010/ Download the article free of charge
rates in an oxygen-hydrogen-nitro- issue15/news from the Science in School website
gen oxide atmosphere. Journal of (www.scienceinschool.org/2010/
Geophysical Research 76(30): 7311- Web references issue17/ozone), or subscribe to
7327. doi: 10.1029/JC076i030p07311 w1 – The British Antarctic Survey is Nature today:
Farman JC, Gardner BG, Shanklin JD responsible for the UK’s national www.nature.com/subscribe
(1985) Large losses of total ozone in scientific activities in Antarctica. Nature has also published a collection
Antarctica reveal seasonal See: www.antarctica.ac.uk of articles that have advanced our
ClOx/NOx interaction. Nature 315: w2 – The Advanced Global understanding of the stratosphere
207-210. doi: 10.1038/315207a0 Atmospheric Gases Experiment, and the ozone layer, or told the
The article is freely accessible on the AGAGE, is a NASA-sponsored ini- story of the discovery, some of
Nature website (www.nature.com) tiative that has been measuring the which are freely available. See:
or via the direct link: composition of the global atmos- www.nature.com/nature/focus/
http://tinyurl.com/2wemxhn phere continuously since 1978, ozonehole



Science topics

NASA images courtesy of the Goddard Space Flight Center Scientific Visualization Studio

The Ozone Depletion website by scien-
tist and author Rod Jenkins contains
comprehensive information:
www.ozonedepletion.info
The website of the United Nations
Environment Programme’s
OzonAction branch provides a
1974 1994 large collection of data and
information about ozone and
the Montreal Protocol. See:
www.unep.fr/ozonaction
See also the pages of the United
Nations Environment Programme
Ozone secretariat, in English, French
and Spanish: http://ozone.unep.org
2009 2020
NASA offers two online videos of
atmospheric developments over the
Arctic, as measured with the Upper
Atmosphere Research Satellite
(UARS).
You can watch the increasing
concentration of chlorine nitrate
2040 2060 in February / March 1993. See
Ozone concentration (Dobson units) www.nasaimages.org or use
the direct link:
http://tinyurl.com/2w6wgh4
0 100 200 300 400 500 600
This video shows the formation of
polar stratospheric clouds. See
This is how the ozone layer would look if CFCs had not been banned www.nasaimages.org or use the
direct link:
NASA’s Ozone Hole Watch page eruptions. See: www.gcrio.org or http://tinyurl.com/33dfn6e
offers historical ozone maps, ozone use the direct link: In addition, NASA has published
facts, an ozone-related multimedia http://tinyurl.com/2wpvf9r images of a season in the life of the
gallery, a collection of teaching Introduction to Atmospheric Chemistry ozone hole. See: www.nasa.gov
modules about ozone-related by Harvard University’s Professor /vision/earth/lookingatearth/
topics, and more. See: Daniel J Jacob, which is freely 25TOMSAGU.html
http://ozonewatch.gsfc.nasa.gov accessible as a PDF, contains a For the complete list of climate-related
The University of Cambridge, UK, section on ozone, including the articles published in Science in School,
diagram ‘Chronology of the ozone
has compiled a virtual tour of the see: www.scienceinschool.org/climate
hole’ (chapter 10.3.3). See:
ozone hole, its history and science.
http://acmg.seas.harvard.edu or
The tour is available in English,
use the direct link:
French and German. See:
http://tinyurl.com/39vhy6a Dudley Shallcross is a professor in
www.atm.ch.cam.ac.uk/tour or use
Ozzy Ozone is a United Nations atmospheric chemistry and Tim
the direct link: Harrison is a school teacher fellow at
Environment Programme website
http://tinyurl.com/2wpvf9r the School of Chemistry, University of
offering educational cartoons,
The 74 scientists who attended the games, a glossary and more – Bristol, UK. For more information
panel review meeting for the 2002 including downloadable education about the post of school teacher fellow,
ozone assessment in Les Diablerets, packs with student and teacher see Patterson (2010).
Switzerland, published 20 Questions handbooks for both primary and
and Answers about the Ozone Layer, secondary school. All material is
including the contributions of cycles available in English, French, and
of solar activity and volcanic Spanish. See: www.ozzyozone.org


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